Dementia with Lewy Bodies
Dementia with Lewy Bodies (DLB), also known as Lewy Body dementia and cortical Lewy Body disease was first able to be characterised in the 1980's when immunological stains were developed that allowed identification of Lewy bodies in the cortex. Perhaps because of its recent characterisation it is often still thought by many as a subtype of Alzheimer's disease. Indeed many past descriptions of the characteristics of Alzheimer's disease are suspect.
It is a histological diagnosis which may be suspected in life. These histological changes are present in up to 20% of recent elderly dementia post mortem series. The changes have been described in those without evidence of cognitive impairment. While cortical Lewy bodies are found in those with dementia due to Parkinson's disease, often an arbitrary absence of cognitive impairment in the first year of parkinsonism is used to distinguish a secondary dementia from Parkinson's Disease from DLB.
The clinical picture often includes:
- Fluctuations in cognition over relatively short periods.
- Excessive daytime drowsiness
- Staring into space
- Episodic disorganized speech.
- Visual hallucinations
- Often complex
- Non-visual hallucinations also seem more common than in Alzheimer's disease
It can also be suggested by:
- Neuroleptic sensitivity - can be single dose
- Absent attacks unresponsive to anti-epileptics
- Recall may be poorer than storage of memory
- milder than that usually found in Parkinsons disease with dementia (it is now possible to distinguish the two conditions by in vivo PET imaging)
- but with postural instability
- behavioural rather than physical dependency being dominant
- symmetrical parkinsonism
- poor tolerance of treatments for parkinsonism. Often only levodopa preparations can be tolerated and many easily hallucinate or develop worse confusion on quite low doses.
- there does seem to be a response in some to acetylcholinesterase inhibitors at the risk of exacerbating parkinsonism
- Cortical Lewy bodies
- Β-amyloid deposited around blood vessels (cf Alzheimer's disease)
Most non-specific and are used to exclude other pathology.
- PET scanning with multiple ligands has been demonstrated to be more specific but is only presently a research tool.
- 18F -FDG Glucose PET cortical uptake decreased in all dementia (and can demonstrate pre-clinical abnormalities)
- 11C -PIB PET shows high levels of cerebral amyloid, typically half the amount of Alzheimer's disease and much more than the non-amyloid dementias such as Parkinson's Disease with dementia (PDD).
- FD-CIT shows a distinct loss of dopamine transporter binding in either Dementia with Lewy bodies or Parkinson's disease with dementia which is not present in Alzheimer's disease.
- SPECT with 123I-FP-CIT (123I-2beta-carbometoxy-3beta-(4-iodophenyl)-N-(3-fluoropropyl) nortropane may become part of the revised clinical criteria for diagnosing the condition.  It is also complimenting FDG PET in narrowing the differental diagnosis and closer to routine clinical application
- Regrettably the post mortem correlation also shows that if as well as DLB you also have mixed vascular dementia or Alzheimer's Disease PET findings can be confusing in life.